Catalytic isomerization process



DeC- 23, 1947 J. M. WHITEILEY, JR., ETAL 2,433,079

CATALYTIG I SOMERIZATION PROCESS 3 Sheets-Sheet 2 Flled Sept. 30, 1939 l s l f I DCC' 23, 1947- J. M. wHlTELEY, JR., ETAI. 2,433,079

CATALYTIC ISOMERIZATION PROCESS I Filed Sept. 30, 1939` 5 Sheets-Shet I5 F/G-S' f 22S' fam Patented Dec. 23, 1947 CATALYTIC IsoMERIzATIoN PROCESS James M. Whiteley, Jr., Aruba, Curacao, Dutch West Indies, and Charles S. Lynch, Fanwood, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application September 30, 1939, Serial No. 297,198

9 Claims. l

The process of the present invention relates to the isomerization of hydrocarbons, and, more particularly, to the conversion of normal or straight chain parafnic hydrocarbons into isoor branched chain paraflinic hydrocarbons by catalytic means. It is known that hydrocarbons, in particular the straight chain paraflins, may be isomerized into branched chain paraifns in the presence of various catalysts of the Friedel- Crafts type, such as aluminum chloride, aluminum bromide, molybdenum trisulfide, ferric chloride, zinc chloride, and the like, with or without the addition of promoters. The paraimc hydrocarbon products possess different physical and chemical properties and are chiefly branched chain in character. Heretofore various difficulties have been encountered in attempting to place this operation upon a commercial scale. The Friedel-Crafts type catalysts are not easily controlled in their reaction. Furthermore, up to the present time a continuous liquid phase operation has presented certain inherent difficulties due, principally, to the problem of catalyst degradation and formation of undesirable byproducts in major amounts. Furthermore, the ease of control of the operating conditions has not been perfected. As a result, truly continuous processes have not been operated on a commercial scale.

The success of the present invention lies in the fact that it has now been made possible to effect an economical continuous isomerization process upon a commercial scale employing a liquid phase operation. Troubles incident to the mechanical agitation which has heretofore been thought necessary have been substantially completely eliminated and the operating variables are now easily and readily controlled. It has been found that, for example, a moving bed type of catalyst in which the ratio of catalyst to hydrocarbon feed is maintained large and where in a specified thruput is maintained under the operating conditions successfully accomplishes these advantages. By operating according to the process of the present invention, it has .been found to be unnecessary to shut down the unit in order to effect a replacement of the spent catalyst.

It is an object `of the present invention to effect an economical catalytic isomerization process, particularly with reference to the lower paraiiinic hydrocarbons, and to carry out such a invention to provide a moving bed of isomerization catalyst and to continuously feed straight chain parains containing at least four carbon atoms per molecule under isomerization conditions in contact with said bed. Another object of the invention is to carry out a continuous liquid phase commercial isomerization process using a plurality of isomerization reactors connected in series or in parallel so as to make use of a large catalyst mass with a maximum ellicency and with a maximum production of branched chain paraiinic hydrocarbons which are known to be useful in various refinery operations and in some cases as gasoline constituents per se. Still another object of the invention is to produce branched chain parafns from straight chain parafns by isomerization While employing apparatus enabling operators to more accurately control the reaction conditions of the process.

In order to accomplish these objects, as well as other objects which will be apparent from a full understanding of the invention to be more fully hereinafter described, it has now been found that excellent yields of the desired isomeric hydrocarbons, in particular isoor branched chain parans of four or more carbon atoms per molecule, may be obtained by employing a relatively large ratio of catalyst to straight chain hydrocarbons fed to a reactor at any one time. In other Words, the objects of the invention may be accomplished by feeding hydrocarbons into stationary or moving bed type reactors substantially filled with a large mass of catalyst and allowing the feed stock to percolate thru the bed under the isomerization conditions desired.

The isomerization may be eifected over a wide range of conditions of temperature, time of contact, catalyst form, concentration of promoter, etc., all of these factors being interrelated. In general, temperatures between about 30 F. and about 400 F. may be employed, although at temperatures above 300 F. there is apt to be some decomposition in the formation of lower hydrocarbons with a lower number of carbon atoms. However, the presence of hydrogen formed in situ or added from extraneous sources has a tendency t0 suppress such decomposition reactions. In cases where normal butane is employed, a temperature range between about room tmeperature and about F. is advantageous. Good yields may be obtained Within these ranges using a contact time of from about 10 seconds to about 15 or 20 hours depending upon the temperature and the form of catalyst 3 employed. In general, space velocities of from about 0.2 and about 5.0 volumes of straight chain parafn per volume of catalyst per hour are employed.

Various promoters may be employed in the reaction, for example, hydrogen chloride, hydrogen bromide, and other hydrogen halides, lower alkyl halides, for example methyl chloride or bromide, ethyl chloride or bromide, butyl and amyl halides, and the like. In some instances it is even advantageous to add free halogen to the reaction. The promoter is aded in an amount equal to from about 0.5 to about 25%, preferably between about 2 and about 10%, based upon the parain feed stock.

As will be more fully hereinafter explained, the promoter, for example, hydrogen chloride, may be employed in excess amounts so that the reactor is not completely lled with liquid phase components but also contains a small gas phase above the liquid portion thereof. In this way, when employing the partial pressure of the hydrogen chloride, the concentration of the hydrogen chloride in the liquid phase is more readily controlled. At 200 F. an increase in pressure of 50 lbs. will result in a hydrogen chloride concentration of 2% in the liquid phase. An increase in pressure of 100 lbs/sq. in. corresponds, roughly, to about 5% hydrogen chloride in the liquid phase and an increase in pressure of 150 lbs. corresponds to about 8% of hydrogen chloride in the liquid phase. These data apply when employing normal butane as the reactant. Similar data on the solubility of hydrogen chloride in normal pentane at 75 F. show that the solubility is quite high and is proportional to the applied pressure of hydrogen chloride.

From the very nature of the process herein described the catalyst vconcentration is necessarily quite high. A concentration between about 100% and about 1000% and higher is usually employed. Fresh catalyst is added to the bed continuously or intermittently, depending upon the rate at which the catalyst becomes substantially completely degraded. The spent or partially spent catalyst is removed in like manner from the bottom of the bed in order to make room for the newly added catalyst.

The process is applicable to the treatment of normal butane, normal pentane, normal hexane, normal heptane, normal octane, and the corresponding higher homologues or the paraffin series. It is within the scope of the present invention to also employ mixtures `0f two or more of these paraiiinic hydrocarbons. Likewise, the invention is applicable to the treatment rof the 'straight run naphthas of relatively low octane number which are composed predominantly of normal paraflnic hydrocarbons. Such isomerization 'treatment as herein `described materially increases the octane number of these naphthas. The inventionis likewise applicable to the treatment ci eld butanes, parainic mixtures resulting from the removal of olenic constituents of refinery C4 C5 cuts, waste gases of p'araflinic nature 'evolved from thermal and/or catalytic allyl'ation and polymerization units, and similar paraiinic hydrocarbons. In general, any hydrocarbon mixture composed predominantly 'of saturated straight chain compounds is suitable as a feed stock for the process herein outlined.

The process is chiefly directed `to continuous operation although it is to be distinctly understood that a batch type reaction is entirely 'feasible when employing `a percolation process wherein 4 normal parafns are percolated thru a large bed of isomerization catalyst mass under isomerization conditions.

The process of the present invention contemplates the carrying out of the reaction in the liquid phase. Normal butane, when employed as a reactant, requires the use of superatmospheric pressures to maintain the reaction in liquid phase under the conditions of operation obtaining. Normal pentane may likewise often require the application of superatmospheric pressures in order to maintain liquid phase operation under the conditions obtaining.

In order to more fully understand the process of the present invention, reference may be had to the drawings which are more or less purely diagrammatic representations in sectional elevation of suitable flowplans showing some structural detail. The apparatus is capable of quite wide modification to suit the exigencies of any particular isomerization process. However, the drawings will be described with reference to the use of aluminum chloride as the catalyst, hydrogen chloride as the promoter, and normal butane as the feed stock.

Fig. l represents a single reactor and a series of stills and other conventional units for separating the reacted mixture from the catalyst and segregating the desired products from lthe undesired products and unreacted reactants. Fig. 2 is a more or less diagrammatic representation of a series of reactors similar to that disclosed in Fig. l. Fig. 3 represents a diagrammatic presentation of still a second type of reactor applicable for carrying out the general process of the invention.

According to the process as carried out using a single reactor, fresh catalyst, for example aluminum chloride in lumps or granules or deposited on an inert carrier, such as pumice, bauxite, fullers earth, kaolin, diatomaceous earth, Filtrol or impregnated on silica or alumina, is introduced into reactor i thru hopper I'I controlled by pipe I5 and valve I5 thru the intermediate pressure chamber I4 and from thence into reactor 'I by means of pipe I2 controlled by valve I3, thereby substantially lling reactor 'I between the two plates represented by numeral 23. Intermediate pressure chamber I4 is maintained at atmospheric pressure while being lled with fresh catalyst by closing pressure valve d1 in line '56 leading from the superatmospheric system and opening valves 2! and 5 in line 48. Upon being iilled, chamber I4 is subjected to the pressure of the system by closing valves I6 and 2I and opening valves 5 'and 41. Once the pressure is equalized, valve I3 is opened and the catalyst is introduced into reactor 1. Normal butane is introduced by means of pipe 2 into preheater 3 together with fresh activator, for example, hydrogen chloride, which is introduced into pipe 2 by means of lines l2 and 'M controlled by valves 'I3 and 15 respectively. Valve 22 is open and the mixture is conducted into reactor I by means of pipe 5A and a suitable dispersion device II. Sulicient superatmospheric pressure is maintained in the system to insure that the normal butane remains in the liquid phase, As the liquid ascends and percolates thru the catalyst bed, the reactor is maintained at the desired reaction temperature by means of temperature jacket 8 into which steam or some other suitable heating medium is introduced by means of inlet 9 'and withdrawn by means of outlet I0. As the reaction proceeds, the spent catalyst is withdrawn by means of incline section |8 into outlet pipe I9 controlled by valve 20. The efliuent from reactor 1 may be withdrawn thru either pipe 24 controlled by valve 2'5 or pipe 23, depending upon whether or not a partial pressure of hydrogen chloride is maintained in the upper portion of the reaction chamber. Valve 25 remains closed in this latter instance and the reactants are withdrawn thru pipe 28 and may be conducted by means of pipe 26 controlled by valve 2`|r into line 3l and introduced by means of pump 32 into a suitable settler or lter device 36 by means of line 34 thru open valve 35, valve 33 remaining closed. On the other hand, if the rate of conversion is not sufficiently rapid, the eiluent from line 28 may be reconducted by means of line 29 thru pump 3c thru open valve 6 back to line 2 and reintroduced into the reactor for further conversion to the branched chain paraffin, namely, isobutane, valve 2l remaining closed. If the reactor is operated Without a substantial partial pressure of the activator, for example, hydrogen chloride, the eilluent from line 24 thru open valve 25 may be returned thru line 29 as described, or pump 32 may be placed in operation and the eiiiuent introduced into the settler or filter unit 36 for the removal of the last traces of the catalyst which may be suspended in said eluent. The filtered or settled product is introduced into still 43 by means of pipes 39 and 4|, valves 46 and 42 remaining open. On the other hand, if the eiiluent from reactor l is of sufcient clarity and contains very little catalyst in suspension, settler or filter unit 36 may be omitted by closing valves 35 and 46, and pipes 3| and 4| may be placed in operation by opening valve 33. The clear product introduced into still 43 is separated into unreacted reactants owing from the still thru pipe 44 controlled by valve 45. The overhead product passing thru line 49, cooler 16, into receiving tank l1 may be either returned to still 43 to serve as reflux by means of pump 18 and line i9, or it may be conducted by means of line 56 into the secondary still or fractionating column 5| where the desired product, isobutane in the present instance, is withdrawn thru line 52 controlled by valve 53, and the lighter products, for example, any propane which may have been formed as well as hydrogen and hydrogen chloride, are conducted from still 5| thru line '54 into cooler 55. rIhe condensate is conducted by means of pipe 56 to settling drum 5l. A portion of the condensate in receiver 5l may be returned to still 5| to serve as reflux by means of lines 58 and 6|, valve 66 remaining closed and valve 62 being opened. Pump 63 is employed to effect a flow of the condensate for reux purposes. The remainder of the condensate may be either withdrawn thru line 59 controlled by valve 64 or line `66 controlled by valve 6l. However, the greater portion of the hydrogen chloride and hydrogen will be evolved from receiver 5l thru line 64 controlled by valve 65. IThis may either be bled from the system or returned to the reactorl 1 by means of lines 68, l and '|4 controlled by valves 69 and l5 by means of pump The unreacted reactants from still 43 are likewise returned to reactor l by means of lines i6 and 'M controlled by valve 15 by means of pump '|I. The separated catalyst from the settler or filter unit 36 is withdrawn thru line 3l controlled by valve 38. This separated catalyst may either be discarded or if not entirely spent, may be returned to the catalyst zone in any suitable manner. Numerous details of construction have been purposely omitted from the drawing as represented by Fig. 1 for the purpose of simplicity in illustrating the process of the present invention. Obviously, valve 42 is in eiect a pressure release valve. Numerous pressure recording instruments, flow regulators, and the like are required in actual operation but it is felt that those familiar with the details of operation are suiiiciently skilled to know the correct placing of these instruments.

Fig. 2 discloses a series of three reactors, reactors A, B and C, so arranged as to provide a plurality of types of operation. The process of separating the desired product from these reactors ,is substantially identical with that disclosed in Fig. 1 wherein a single reactor has been described. With respect to reactors A, B and C, the elements are numbered so that the same element in the reactors is described by the same number as that given for that element in Fig. l. No further details of the construction of the reactors is therefore deemed necessary. It should be distinctly understood in describing the operation of reactors A, B and C that more than three reactors are obviously included within the scope of the invention, it being suiicient, for the purposes of illustrating the invention, to describe in detail the inter operation of these three reactors.

The three reactors may be run in parallel so that each reactor operates as a unit unto itself similar in operation to the reactor described in Fig. l. The feed stock enters the system thru pipe |00 controlled by valve mi. The feed stock then enters a series of pipes as represented by numerals |08, H9, ||2 and 4 controlled by valves H3, ||5 and |89. For parallel operation of the reactors these valves are opened. The partially used activator, hydrogen chloride and/ or the unreacted reactants, for example, normal butane, returned from the separation system and fresh activator are introduced into these same lines, thereby effecting the introduction of the mixture into pipes H6, H8 and |28 controlled by valves ||1, H9 and |2| respectively. The fresh activator may be separately introducedby closing valve and opening valves |33, i4! and |43, allowing lineslliZ, |33, |46 and |42 to carry the fresh activator to the reactors. The feed stock is then introduced by means of pumps |57, |22 and |23 and lines |64, |85 and |95 respectively into preheaters 3l, 36 and 99, valves |44, |45 and |46 remaining closed. The effluent from the heaters is conducted by means of lines |64, and |66 into lines `'32, 86 and '98, valves 83, 3l and 5| remaining open and valves 85, 89 and 93 remaining closed. Valves 94,- 35 and 96 are also opened, thereby permitting the preheated reaction mixture to enter the reactors A, B and C thru line 5 of each reactor, valves |39, |4| and |43 remaining closed. The eiuent from reactors A, B and C is conducted by means of line 24 controlled by valve 25 in each reactor into lines |26, |39 and |34 from whence it may be conducted to the flashing tower of a separation system or to a settler or lter unit similar to that represented by numeral 36 in Fig, l. On the other hand, if the rate of conversion has not been sufficiently great to eiect a substantial maximum percentage yield of isobutane, valves |25, |29, |33 and |36 are closed, valves |44, |45 and |46 may then be opened, and by means of pumps |01, |22 and |23 the partially reacted mixture may be returned to the preheaters and reconducted to reactors A, B and C respectively as heretofore described. Although Fig. 2 does not disclose the operation, it is within the contemplation of the invention to provide each reactor with a draw-01T line similar to line 28 of Fig. l thereby permitting theV operation kof reactors -'A, B' and C, using a partialpressureof hydrogen chloride sufciently vgreat Ytomaintain a portionfof the reaction in the gaslphase.

Reactors A, B and C mayalso'beoperatediinfa series arrangement. This operation is conducted by ypermitting all of the fresh vfeed entering line controlled by valve lill to pass into :line Ei controlled by valve The recycled vunreacted reactants and activator are conducted'thru lines ||4, |f|2 and `lli! intoline |15, valve ltl remaining closed unless it is desired tointroduce fresh activator, in which case line |118 is employediand valve ||'|`is opened. Valves 83,181 and 9| remain closed so that the eiuentfrom'heaters 91,98 and. 99 passes thru lines 134,84, 135,153, |06 and 182, valves 85, g5, 89, EG and 93' remaining'open. The effluent from the preheater preceding Vreactor A (not shown) enters reactor A thru 'linell controlled by valves 8| and 94. Theeluentfromfthe reactors enters lines |25, |310 and |34, .valves 12.5, |28, |33 and |36 beingclosed, and valves |21, rl'l and |35 being open. If reactor AB is the initial reactor in the series arrangement, valve'li44 remains closed. However, if a preheater is in operation ahead of reactor A, valves |244, |45 and 1415 remain open and pumps ll, |22 and Y|23 are operated so as to permit the flow of reaction mixture thru the respective preheaters intothe next -succeeding reactor. The effluent from reactor D (not shown) or the effluent from Lany-'designated fina-l reactor, for example reactorC twh'ere heater 99 is omitted from operation), is permitted to'pass to the conventional fractionation columns vand settling Zones as representedin Fig. 1 inorder to separate the desired productynamely, isobutane, from the reacted mixture. This effluent flows thru line |34 controlled by valve |35, valve 'l it in such an instance remaining closed.

This arrangement of a, plurality of reactors in series for accomplishing the isomerization reaction may also be modified so as to attaina maximum catalyst efficiency during continuousoperation of the process7 for example, preheaters @1,98 and 99, as well as the heat jackets 8 on reactors A, B and C, may be maintainedat different .temperature levels so as to accomplish adistinctLtemperature gradient between the several reactors and operated in accordance with the process outlined in the copending application of Charles S. Lynch entitled Isomerization process,V SerialNo. 292,838 filed August 31, 1939, now Patent 2,280,710. Furthermore, it is possible to carry out the series operation ofthe plurality of reactors so as to employ a less reactive catalyst bed amongthe several reactors as a pretreatment reactor for the feed stock, thereby permitting the removal of ,impurities and undesirable constituents of the feed stock by polymerization methods. It :is known that olens, aromatics, and theilike, are distinctly deleterious to the economical and smooth functioning of an isomerization process for paramnic hydrocarbons. In the ordinary operation of the series process, reactors A, B and C will carry out the isomerization reactor in proportion to theactivity of their catalytic contents, thus where a fresh feed is introduced into reactor A, alarger percentage of the conversion of normal butane to isobutane will be effected therein than in any subsequent isomerization reactor. Consequently, the catalyst in reactor A undergoesfdegradation and decomposition to a greater extent in reactor A than .in the subsequent reactors. It is therefore .Within the contemplation ofthe present; invention to permit the feed stock-to continuously be'introduced intoreactorA and to then provide means for introducingthe eiliuent .from-reactor A into some'subsequentreactor in which the catalyst'activitytis substantially greater although it is not intendedLthatithisreactor be the next subsequent reactor. In Vother Words, the eilluent from reactor A Would'irst'be runthru reactor C prior to introducing ,the same into .reactor B, or where a series of `a large number of reactors were employed, thepath of the feed stock might be so controlled aslto run ythru reactor A, then reactors E, D,C'andfB in .that order. In other'words,'the isomerization conversion rate, by suitable manipulation of the `.feed stockeither unreacted or partially reacted, vcan vbe so controlled in its manipulations so: as toY accomplish a more or less'uniformcatalystI degradation in all of the reactorszin series rather'thanhaving a major portion of the conversion effected in the initial reactor into Whichthe .unreacted feed stock isintroduced. A more uniform `catalyst .degradationin each of the reactors is-desira'ble for the reasonithat the introduction of 'freshcatalyst and the removal of spent'catalyst from each reactor, if carried out: on amore-or less uniform continuous or semi-continuousabasis, lends itself to greater ease of operation and supervision.

Infsome instances itmay'be desirable'to effect a partial regeneration of `the catalyst activity in anyone or group ofreactors. `It so happens that itis sometimes advantageous, where a catalyst has dropped tota-low efficiency yet has notbeen completely `spent or degraded, to regenerate or revivifyfthatcatalyst. In such an instance, a reactor may be by-'passed without interrupting the continuous operation of the other reactors either in parallelvorin series operations. For example, if fit is desired to shut down reactor B and yet continuefthe operation of reactors A and C, valves and 25 vare closed. lIn series operation lthe eluent from reactor lA yis conducted thru pump |111 by openingvalves |21 and |44 thru preheater 91 into line-84 by means-ofiopen valve 85, valve 83 remaining closed. `Valves81zand'89 are opened andv by'meansof-lines 8E and 8'8'the eflluent from reactor A, preheated by means of heater 191, is introduced into line v5A of 'reactor C by opened valve` 9S, vval-vell remaining closed. In parallel operationV of'reactors 'A and` C with reactor'B shut down, valvesii 81,855,953, H9 and`|45 are closed as'Well asfvalves 2'5 and-95. The effluent from reactor 'Aenters line |26 by'means of open valve #-21, passes thru line |28 by means of open valve |:29andline'l39 by means'ofopen Valve |3| into lines |32.and :|34 by means of open valves |33, |35 and |36 and from'there into the separation and settling tanksthe effluent from reactor C likewise joiningithe-eifluent from reactor A in line 13A-and passing thru open valves |35 and |35.

4In ordertoregenerate the partially spent aluminum chloride mass .in reactor B, fresh acti- Vator, for example, vhydrogen chloride, is introduced-intoline 32 `and from there it is conducted by meansiof line |411 and open valve I4| into reactor -B whereit is allowed to Contact the partially 'spent catalyst mass. The evolved hydrogen chloride may-then`be taken from the system thru the pressure'equalizing system employed in introducing'the 'freshcatalyst into the reactor, that is, linesfdt and 43.are employed by opening valves 41. and f2 I .and permitting valvev to remain closed.

'Itfis sometimes lfeasible to permit the ow of reactantsithru any specific reactor for longer periods 'f'timethan can be accomplished by oncethru operationina given reactor. Fig. 2, therefore, discloses a provision for the recycling of the partially isomerized parafnic hydrocarbon reactants by permitting the flow thru Ypipes |114, 185 and |86 to be partially diverted thru pipes 82, 86 and 811 respectively by valves 83, 81 and 91 being partially opened. In such an instance, valves 121, 131 and 185 are open and valves 125, 129 and 133 remain closed in a series type of operation. Valves 81, 85, 88 and 83 remain partially open to permit the passage of the reacted material into the next reactor. By operating in this manner it is possible to retain more of the feed stock introduced into any specific reactor for a longer length or time in that reactor or until the rate of conversion desired has been attained in that reactor. This is more or less a provision for a continuous recycle feature to the reactor to permit the desired length of time to eiiect the desired conversion to take place,

Fig. 3 presents a diagrammatic illustration oi still another type of reactor suitable for carrying out the process of the present invention. The catalyst from catalyst hopper 228 is introduced into a pressure chamber 225 by means of pipe 226 controlled by valve 221. The pressure is then increased to that maintained in the reaction zone by opening Valves 235 in line 234 and 231 in line 23S, valve 239 in line 238 remaining closed. Once ,the pressure in the chamber 225 has reached that of the reaction zone, valve 231 is closedand valve 224 opened to permit the catalyst to pass thru line 223 into the cyclone separator 218. The catalyst, when operating the process according to the apparatus disclosed in Fig. 3, should preferably be a fairly nely divided powder of the order of 100 to 200 mesh. The catalyst in cyclone separator 218 is conveyed to reaction chamber 286 by means of a screw conveyer or slurry pump represented in the drawing as element 219. This screw or pump may be driven by any suitable mechanical means, for example, a motor 222. Fresh feed is introduced into the system thru line 282 controlled by valve 283. Fresh activator is introduced into the system thru line 232 controlled by valve 233. The two streams are united and enter a preheater 285 thru pipe 2114 which in turn empties into the bottom of reactor 288. A pump (not shown) maintains a suiiicient velocity of flow of the fresh feed, which is in the liquid phase, to create a swirling motion within the reactor 2136 equipped with spiral baffle plates 218 so that the catalyst powder entering by means of screw conveyer or slurry pump 219 is taken up as a slurry in the liquid reactant and carried thru the series of bailles upwardly for the desired time. Reactor 285 is equipped with a heating jacket 281 provided with inlet 289 and outlet 288 whereby it is possible to maintain the desired reaction temperature during the residence of the catalyst and reactants in the reactor 285. Any suitable heating medium, such as heavy oil, steam or flue gases, and the like, may be employed as a heating medium in the jacket 2111. The eiiluent from reactor 286, which consists of a slurry of small amounts of decomposition products, isoparaflins, catalyst and spent catalyst, together with small quantities of hydrogen, is then withdrawn by means of pump 212 and may then take one of two courses. If the reaction has not suiciently progressed within the reactor 288, the partially reacted mixture may be returned to the reaction zone thru line 216 by opening valve 211. Onrthe other hand. if the mixture is suciently isomerzed, valve 211 remains closed and valve 215 is open thereby permitting the slurry to pass by means of pipe 214 into the catalyst separator 2 I 8. In practical opere ation it is desirable to partially open both valves 215 and 211. In catalyst separator 218 the slurry is broken, the catalyst mass settling Ato the bottom and substantially clear super-natant liquid is withdrawn by means of pipe 229 for further processing to isolate the desired product. The spent catalyst, having settled to the bottom of separator 218, may either be returned to the reactor 288 by means of screw conveyer or slurry pump 219, or if it has reached a point where it is no longer useful in the reaction because of degradation, it may be withdrawn from the system by means of pipe 220 controlled by Valve 221. The product withdrawn thru pipe 229 may be subjected to a ltering operation or other suitable separating operation wherein the last traces of the catalyst are separated from the hydrocarbon product. Said hydrocarbon product may then be subjected to fractionation treatment to effect a separation of the desired isomers from the product. Unreacted reactants and activator may then be collected and returned to the reactor 206 thru line 238 controlled by valve 23|. In operating pressure chamber 225, it is necessary, before reiilling said chamber with fresh catalyst, to reduce the pressure to the pressure of the catalyst hopper 228. This is accomplished by closing valve 235 and opening valves 231 and 239. Valve 239 is then closed, valve 221 is opened, pressure chamber 225 is allowed to iill the catalyst, valve 221 is then -closed and pressure from the system connecting the reactor is permitted to enter the chamber by means of valves 235 and 231 as heretofore described prior to introducing the catalyst in chamber 225 into the catalyst separator 218 by means of line 223 controlled by valve 224.

A single spiral baffle tower reactor has been described. However, it is within the contemplation of the invention to operate simultaneously and in inter-connection with each other a series of spiral baffle tower reactors, the operation of these being quite similar to the operation of the series of reactors described in Fig. 2 in connection with the single reactor described in Fig. 1. However, no difliculty is encountered in assembling a single reactor of the type disclosed in Fig. 3 into a series of inter-connected reactors capable of series and parallel operation as described with reference .to the reactor of Fig. 1 in Fig. 2. It is to be realized, of course, that the actual catalyst concentration in a slurry is limited to amounts of the catalyst such that a slurry will be maintained. Those operating a process as described in Fig. 3 are well aware of the fact that a suiiicient velocity of the feed entering the reactor must be maintained to pick up and carry in suspension the powdered catalyst entering the reactor by means of the screw conveyer or slurry pump. It is therefore not possible in this type of apparatus to maintain a catalyst concentration as high as may be maintained in connection with the bed type of operation. However, the results obtainable with the baflie tower slurry process are proportionately as excellent as those obtained with the -bed type percolation method, v

However, it should be distinctly understood that the process of the invention is not limited to any particular type of apparatus since it is only necessary, in carrying out the process of the present invention, to eiect the isomerization reaction in the presence of extremely large quantities of catalyst per unit volume of paraffinic reactant.

1 1 Any apparatus, therefore, which is capable of accomplishing this type of operation, will be entirely suitable for carrying out the process of the present invention.

In order to more fully understand the exact nature of the present invention, the following examples are given:

Example 1 A reactor was filled with about 83 gms. of a commercial grade of A1C13 lumps. About 135 gms. of normal pentane, together with a small amount of HC1 was percolated through this bed at a feed rate of about 0.9 v./v./hr. at a temperature of about 76 F. Isopentane was formed to the extent of about 6%. About 8% of the normal pentane was reacted.

Example 2 In a continuous unit, about 400 cc. of a commercial grade of AlCls granules were charged to a reactor, the entire system being maintained under suflicient superatrnosphericY pressure to insure that the feed stock comprising essentially normal butane remained in the liquid phase throughout the reaction. For about 420 hours the feed stock of normal butane was continuously percolated upwardly through this catalyst bed maintained at from about 150 to about 175 F. at the rate of about 0.5 v./vv./hr. About 20% of HC1 was continuously added to the feed stock. Initially, the yield of isobutane was about 40%, after about 12 hours operation, about 60%, and after 400 hours operation, above 50%. In general, about 12 gallons of isobutane per pound of AlCla charged was obtained. In this particular experiment, no additions of fresh AlClx were made as the run progressed.

Example 3 About 2 liters of a commercial grade of AlCls lumps were charged to a reactor. Normal pentane containingy about- 3% HC1 was continuously percolated through the catalyst bed at a rate of about 0.3 V./v./hr. while maintaining the catalyst bed at about room temperature. After about 5 hours operation, the product produced yielded about 38% of isopentane. After about 3 hours additional at about 2.5 V./v./hr. the yield of isopentane obtained was about 30 The present invention is not intended to be limited to any theory 0r mechanism of operation but only insofar as limited by the following claims in which itis desired to claim all novelty inherent in the invention. The nature and objects of the invention having been thus fully described, what is claimed as new and useful and is desired to be secured by Letters Patent is:

1. A process of isomerizing normal par-aiiin of at least 4 carbon atoms per molecule to produce isoparaiiin which comprises maintaining a continuous circulating stream of normal paraflin in liquid phase and containing hydrogen halide, maintaining a reaction zone within a portion of the said circulatory stream, said zone having therein a bed of aluminum chloride, percolating the normal paraffin through said bed under isomerzation reaction conditions and recovering isoparaiiin from the reacted mixture, the time of contact of the normal paraffin being suflicient to effect substantial isomerization.

2. A process as in claim 1 in which the fresh feed of normal paraiin is introduced into the stream ahead of the reaction zone and in which the reacted mixture is withdrawn from the stream behind the reaction zone and at a point remote from the point of introduction of the fresh feed, the total volume of liquid in the stream being maintained substantially constant.

3. An isomerization process which comprises percolating in liquid phase at least one normal paraffin containing at least 4 carbon atoms and a small amount of hydrogen chloride through a reaction zone substantially filled with granules of aluminum chloride at a temperature between about 40 F, and about 300 F., and recycling at least a portion of the reaction product without separation.

4. Process according to claim 3 in which the reaction zone comprises a moving bed of catalyst whereby during operation of the process spent catalyst is substantially continuously withdrawn from the end of the reaction zone into which the normal parain is fed, and fresh catalyst is substantially continuously fed into the reaction zone at the inlet end of the catalyst bed.

5. Isomerization process which comprises percolating in liquid phase at least one normal paraflin containing at least 4 carbon atoms and a small amount of hydrogen chloride through a reaction zone substantially filled with granules of aluminum chloride at a temperature between about 40 F. and about 300 F., the throughput velocity being sufciently high for the particular temperature used that the extent of conversion of the normal paraffin into corresponding isoparafn is substantially less than the maximum attainable, and recycling all of the reaction products without any separation until the desired extent of conversion is attained.

6. An isomerization process which comprises feeding fresh catalyst consisting essentially of aluminum chloride granules into the top of a vertical reaction tower through which said catalyst descends slowly, withdrawing spent catalyst at the bottom of said reaction tower at a rate corresponding approximately to the fresh catalyst feed rate, maintaining said reaction tower at a temperature between about 40 F. and about 300 F. by means of a surrounding temperature control jacket, feeding into the basev of said reaction tower a liquid comprising a major proportion of normal parain containing at least 4 carbon atoms per molecule, whereby said normal para'in feed passes upwardly through the descending catalyst bed at a throughput velocity high enough under the reaction temperature used that the extent of conversion of normal parafn to isoparaflin is substantially less than the maximum attainable, withdrawing reaction products from the top of the reactiontower and recycling all of said reaction products through the reaction tower until the desired extent of conversion is attained, there being continuously maintained in said reaction tower a small gas phase above the liquid phase, and maintaining in said gas phase a suflicient partial pressure of hydrogen chloride to impart the desired concentration (between about0.5% and 25%) of dissolved hydrogen chloride in the liquid phase for promoting the isomerization reaction.

7. Process according to claim 6 followed, after the desired conversion is attained, by removal of the reaction products from the top of the reaction tower into a still from which unreacted normal paraffin is removed as bottoms and recycled to the reaction tower, and from which still lighter products are taken overhead including isoparaffins formed by the reaction as well as hydrogen halide promoter and reaction products lighter than the isoparain which may have been formed during the reaction, passing said overhead products into a second still from which the desired isoparaffins are withdrawn as bottoms and from which hydrogen halide and products lighter than the desired isoparafns are taken overhead, and recycling at least a portion of said overhead products.

8. A process which comprises continuously percolating at least one normal parafn containing at least four carbon atoms and a small amount of hydrogen chloride through a reaction zone substantially lled with granules of aluminum chloride, in the liquid phase, said Zone being maintained at a temperature between about 40 F. and about 300 F., withdrawing the reaction mixture from said reaction zone, fractionating the desired branched chain paraffin from the reaction mixture and returning hydrogen chloride, low boiling degradation products of the reaction, unreacted reactants and at least a portion of the reaction product to the reaction zone together with the fresh feed.

9. A process which comprises continuously percolating normal butane and a small amount of hydrogen chloride through a reaction zone substantially lled with granules of aluminum chloride, in the liquid phase, said zone being maintained at a temperature between about 40 F. and about 300 F., withdrawing the reaction mixture from said reaction Zone, fractionating the desired branched chain paraffin from the reaction mixture and returning hydrogen chloride, low boiling degradation products of the reaction, unreacted reactants and at least a portion of the reaction product to the reaction zone together with the fresh feed.

JAMES M. WHITE-LEY, JR.

CHARLES S. LYNCH.

REFERENCES CTTED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,169,494 Ipatieff et al. Aug. 15, 1939 1,647,446 Wolcott NOV. 1, 1927 1,716,372 Downs June 11, 1939 2,208,362 Engel July 16, 1940 2,220,092 Evering et al Nov. 5, 1940 2,125,234 Atwell July 26, 1938 1,882,000 Cross Oct. 11, 1932 2,249,366 Van Peski et al July 15, 1941 2,265,548 Schuit Dec. 9, 1941 1,825,270 Jenkins et al Sept. 29, 1931 FOREIGN PATENTS Number Country Date 24,044 India Aug. 23, 1937 193,071 Great Britain Feb. 16, 1923 255,159 Great Britain July 19, 1926 364,665 Great Britain Jan. 4, 1932 OTHER REFERENCES Petrov et a1., Oil and Gas Jour., Feb. 2, 1939, pages 42 and 45. (Copy in Patent Oice Library.) e

Glasebrook et al., J. A. C. S. 58 (1936) 1944- 1948. (Copy in Pat. Office Library.) 

